Do dolphins eavesdrop on the echolocation signals of other dolphins?

It has been suggested that dolphins are able to eavesdrop on the echolocation signals of other dolphins, and, by doing so, are able to acquire object and environmental information without needing to use their own echolocation. This is known as the ‘echoic eavesdropping’ hypothesis. According to the results of one experiment, it appears that this might indeed be something that dolphins are capable of doing. In 1996, researchers working with dolphins at the Living Seas in Epcot (Disney World) performed a series of experiments where one dolphin echolocated on an object while a second dolphin, positioned close to the first, listened in on the echolocation signals that were produced as well as the echoes that returned from the object. When the second (eavesdropping) dolphin was then asked to choose which object the first dolphin had just echolocated on, the eavesdropper was able to do so. This was strong evidence that the eavesdropping dolphin was receiving object information from the echoes produced by the other dolphin without needing to engage its own echolocation. Many scientists have speculated as to how an ability to eavesdrop on the echolocation of other dolphins might influence the way dolphins behave in the wild. For example; perhaps dolphins swim close to each other and in synchrony with their heads aligned so as to listen in on each other’s echolocation. Unfortunately, almost no data have been collected from wild dolphin species in order to see if this might be the case.

In order to find out if dolphins might indeed be listening in on each other’s echolocation, Justin Gregg began cataloging data to test for echoic eavesdropping starting in 2004. Utilizing both the MVA and ECD to collect video and audio data, an eavesdropping study was initiated focusing on the population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) around Mikura island in Japan. Some of the questions this study is asking are:

  • Does a dolphin positioned in such a way that echoic eavesdropping should be possible actually engage in behaviors that we assume to be associated with echoic eavesdropping?
  • Will an eavesdropping dolphin remain silent when another dolphin begins inspecting an object with echolocation?
  • Will an eavesdropping dolphin keeps its head aligned with and close to the head of an echolocating dolphin so as to best be able to hear and process the echolocation information?

As we begin to analyze the data we have collected, we will be writing up our results and posting PDF versions of our publications on the DCP website. Don’t forget to check back regularly to see how our research is progressing